The “Pepper's Ghost Illusion” is an illusion technique known for centuries (named after John Henry Pepper, who popularized the effect), and has historically been used in theatre, haunted houses, dark rides, and magic tricks. It uses plate glass, Plexiglas, or plastic film and special lighting techniques to make objects seem to appear or disappear, become transparent, or to make one object morph into another. Traditionally, for the illusion to work, the viewer must be able to see into a main room, but not into a hidden room. The hidden room may be painted black with only light-colored objects in it. When light is cast on the room, only the light objects reflect the light and appear as ghostly translucent images superimposed in the visible room.
Notably, Pepper's Ghost Illusion systems have generally remained the same since the 19th Century, adding little more over time than the use of projection systems that either direct or reflect light beams onto the transparent angled screen, rather than using live actors in a hidden room. That is, technologies have emerged in the field of holographic projection that essentially mimic the Pepper's Ghost Illusion, using projectors as the light source to send a picture of an object or person with an all-black background onto a flat, high-gain reflection surface (also referred to as a “bounce”), such as white or grey projection screen. The bounce is typically maintained at an approximate 45-degree angle to the transparent screen surface.
For example, a recent trend in live music performances has been to use a holographic projection of a performer (e.g., live-streamed, pre-recorded, or re-constructed). FIG. 1 illustrates an example of a conventional (generally large-scale) holographic projection system 100. Particularly, the streamed (or recorded, or generated) image of the artist (or other object) may be projected onto a reflective surface, such that it appears on an angled screen and the audience sees the artist or object and not the screen. If the screen is transparent, this allows for other objects, such as other live artists, to stand in the background of the screen, and to appear to be standing next to the holographic projection when viewed from the audience.
Still, despite its historic roots, holographic projection technology is an emerging field, particularly with regards to various aspects of enhancing the illusion and/or managing the setup of the system. For instance, holographic projection systems, in general, often require a fair amount of depth behind the transparent screen in order to properly create the illusion of realism in the holographic projection.